During the last two decades, dengue fever has emerged as a serious health problem in Pakistan. We have analyzed the prevalence, the simultaneous occurrence of multiple serotypes in the patients, and phylogenetic analysis of the prevalent serotypes. The study comprised of blood samples of 18 dengue fever patients from Swat and 5 from Lahore. Using Nested Multiplex PCR, these samples were investigated for the dengue virus serotypes and occurrence of concurrent infection by more than one serotype. Domain III of the DENV envelope protein has been reported to be important for binding with the host cell receptors, and potentially a promising candidate for developing recombinant protein vaccine against dengue. We have amplified and sequenced domain III of the prevailing serotype for its phylogenetic analysis.
We have detected the presence of all four DENV serotypes in these samples, either existing solitary or present along with the others. Of the four DENV serotypes, DENV-2 was found to be the most prevalent, existing in 17 samples and DENV-1 was the least common detected only in two patients. We have identified concurrent infection with more than one serotype in 6 out of the 23 samples studied. Four samples showed the simultaneous presence of two serotypes with one sample having the three serotypes. Surprisingly we have observed the concurrent infection with all four serotypes in one sample, which has never been reported earlier. The phylogenetic analysis suggests that the prevalent serotype (DENV-2) circulating in Swat might have travelled from Lahore. It showed maximum homology with the one reported from India. Our study presents the first report of concurrent infection with DENV-1/3/4 and DENV-1/2/3/4 in a single patient. Thus all the four serotypes are circulating in Pakistan and might be taken into consideration in view of the dengue control.